As was mentioned .net 3.5.1 DOES now support TLS 1.2; but you don’t need the registry changes mentioned by @Paulina’s answer.
I’m using VS 2008 with .net 3.5.30729.4926. All I had to do was:
Add imports:
Imports System.Security.Authentication
Imports System.Net
Add this to my code (C#):
public const SslProtocols _Tls12 = (SslProtocols)0x00000C00;
public const SecurityProtocolType Tls12 = (SecurityProtocolType)_Tls12;
ServicePointManager.SecurityProtocol = Tls12
VB.net version:
Const _Tls12 As SslProtocols = DirectCast(&HC00, SslProtocols)
Const Tls12 As SecurityProtocolType = DirectCast(_Tls12, SecurityProtocolType)
ServicePointManager.SecurityProtocol = Tls12
Culled from: https://support.microsoft.com/en-us/help/3154518/support-for-tls-system-default-versions-included-in-the-.net-framework Note: by defining the const in my code I could ignore everything else in the article including the registry edits and cs files.